At what temperature for a concrete curing is absolutely necessary?

Answer 1

It should be above 40F. Concrete goes through a chemical reaction called hydration, below 40F this process almost stops. Putting concrete blankets over the concrete can allow pours in much lower temperatures. The 40F represents the concrete temperature, while curing it produces heat so the air temperature can be cooler than 40F. Concrete can be poured below freezing but it needs to be protected with concrete blankets to hold in its heat. If the water in the concrete freezes before it is cured than it will definitely fail.